function externalLinks() {
 if (!document.getElementsByTagName) return;
 var anchors = document.getElementsByTagName("a");
 for (var i=0; i<anchors.length; i++) {
   var anchor = anchors[i];
   if (anchor.getAttribute("href") && anchor.getAttribute("rel") == "nw") {
     // anchor.target = "_blank";
     anchor.onclick = function(event){return popupWindow(this, event);}
     anchor.onkeypress = function(event){return popupWindow(this, event);}
   }
 }
}

function popupWindow(anchor, event){
  var keyCode;
  if (event && event.type == 'keypress') {
    if (event.keyCode) {
      keyCode = event.keyCode;
    } else if (event.which) {
      keyCode = event.which;
    }
    // 13 == Return key. 32 == space key
    if (keyCode != 13 && keyCode != 32) {
      return true;
    }
  }
  return !window.open(anchor);
}

window.onload=externalLinks;